Inductance device



April 12, 1927.

A. J. CHRISTOPHER INDUC'I'ANCE DEvfjdE Filed Dec. 13, 1924 L Opar's. I?!

M MVJ m m Patented Apr. 12, v

UNITED STATES ARTHUR J. cnnrsrornnn, or raw YORK, 11. Y., ABSIGNOB Towns-man, ELECTRIC COMPANY, mcoaronnmn, or new YORK, N. Y., A conrosuron or NEW'YOBK.

INDUC'IAKCE DEVICE.

This invention relates to inductance de vices, and purticularlyto transforn'lers or repeating coils of the shell-type, such as are used in telephone circuits.

An object of the invention is tOAPIQVldO a" method of and means for improving the transn'iission efficiency of telephone trans superposed direct current, such as battery supply repeating coils, it is necessaryfor'efficient transmission oftelephone currents that the magnetic field circuits be provided with an air-gap or air-gaps to .prevent an appreciable decrease in the inductance of the windings with increasing values of the superposed direct current. Air-gaps are readily provided in laminated cores made up of lamination sections of different-shapes u stacking the sections so that the joints between successive layers coincide. 1

In such transformers or repeatingv coils, it has been found necessary also to obtain a high degree of impedance balance between i the windings, in order to prevent objection able noise and cross-talk trouble due to unbalance in the circuit.

In accordance with the invention,'a high degree of impedance balance between the windings of an inductance device carrying superposed direct current may be obtained in astructure comprising a shell-'typemagnetic core having air-ga s symmetrically distributed therein an a plurality of equal indings, mounted on the central limb of the core. The symmetrical distribution of the air-gaps in a' laminated core may be readily obtained by using for each layer of thelam1- nated core either C- and straight or'I-shaped laminations, or substantially closed B-type la'minations, and stacking these laminations in aparticular 'way.

For a. better understanding of the invention reference is made. in the accompanying drawings wherein I Fig. lshows a side view partly of the repeating coil embodying the invention; Fig. 2 shows an end view oartly in sec- Y tion, ofthe repeating coil of 1, taken along the line 2-2 of Fig. 1; Fig. 3 illustrates in diagrammatic form the arrange in section 13, 1924. Serial No. 755,640.

ment of the windings of the repeating coil of the invention, when used in a simple telephone circuit;.Fig. 4 shows an arrangement employing C- and .I-shaped laminations which is used in the core of phe repeating coil shown in. Figs. 1 and 2; Fig. 5 shows another arrangement employing substantiall-y. closed 8-type laminations which may be used in the core of the repeating coil shown in Figs. 1 and 2.

Referring in detail to the--.drawin the magnetic core 1 in the particular emb iment of Figs. 1 and 2 is composed'of a plurality of C-shaped pieces and a plurality of strai ht or Lshaped pieces of magnetic materia, such as silicon steel or permalloy, placed together in such a way as to' form a two-mesh magnetic core of the shell-type, having a central limb 2 and outer limbs 3. Laminations forming the parts 2 and 3 are held together by the clamping plates 4, which are attachedthereon by means of screws or rivets 5. The arrangement of the 1 C- and I-shaped lamination sections in core 1 is shown more in detailin Fig. 4.

'Mounted on the central limb 2 of the core 1 is a spool 6 of suitable insulating material, such as phenol fibre, having a separator 7 also of insulating material around its central portion, dividing the spool 6 into two equal ha'lves, on which are wound inner and outer windings 8. The windings 8 comprise two equal primary and two equal secondary windings'one of each being wound around each half of the spool 6.

The metal terminals 9 arranged on a terminal 'plate 10 of insulating material are soldered to and serve as mechanical protection to the lead wires 11 from the windings 8,'coinprising the two primary and the two secondary windings. Only the four leads 11 from the inner windings and the four terminals 9 to which they areattached are shown in Fig. 1. The four leads from the outer windings, which are not shown in thisv view, are attached to four terminals arranged similarl to those shown on the 0pposite side of t e repeating coil.

The terminal plate 10 is attached to one of the. front clamping plates 4, also func-,

tioning as a mounting bracket, by'means of mount ng studs 12. The core 1 and. the

win Bmounted thereon are contained in a s t ease! we e a aine 131 s extension on one of the clamping plates 4 is attached to case-13 by means of a screw 14. The air space 15 between the case 13 and the rear end of core 1 is provided for the purpose of reducing the magnetic flux from the core 1 through case 13, which would tend to unbalance the magnetic circuit of the repeating coil.

As the studs 12 are fastened directly to the mounting bracket 4 of core 1, no mechanical strain due to the weight of the repeating coil parts is placed on the case 13; In use, the core 1 may be grounded through the mounting studs 12 and the panel on which the case 13 is to be mounted.

The arrangement of the windings of the repeating coil of the invention is shown dia grammatically in Fig. 3, which illustrates the coil used as a battery .supply repeating coil in a simple telephone circuit. Referring to Fig. 3, the repeating coil R comprises windings 21 and 6-5, which for convenience in description will be referred to as the primary windings, and windings 43-and 8-7, which will be referred to as the secondary windings. In the particular repeating coil illustrated, windings 21 and 65 are the inner windings, winding 2-1 being wound on one half of spool 6 and winding 6-5 on the other half of 's'pool 6. Windings 43 and 8-7 are the outer windings, winding 4-3 being wound over Wind'- ing 21 on one half of spool 6 and winding- 87 over winding 65 on the other-half of spool 6. v

Terminal 1 of one ofthe primary windings and terminal 3 of one of the secondary windings are connected to the positive pole of battery 16, and terminal 6 of the other primary winding and terminal 8 of the'other secondary winding are connected to the negative pole of battery 16. A subscribers tele phone set S is adapted to be connected to terminal 2 of one primary winding and terminal 5 of'the other primary winding. In like manner, another subscribers telephone set S, is adapted to be connected to terminal 4 of one secondary winding and terminal 7 I of the other secondary winding. An operators telephone set may be connected across the primary side of the repeating coil R for monitoring purposes. A

Now, any electrical disturbance which may occur in the line between either subscribers set S, or S and the repeating coil R will set up disturbing currents in the line'in either direction, as indicated by the arrows, unless the impedance of winding 2-1 is equal to the impedance'of winding 65, and theimpedance of winding 43 is equal to the im pedance of winding 8-7. These disturbing currents may cause objectionable noise in either one or both of the subscribers sets S and S To, reduce this noise to an unobjectiouable amount, it is not necessary that the impedance ratio between the primary and secondary windings be unity. i. e., that the combined impedance of ;Wl l ld. l11gS 21 and 6-5 be equal to the combined impedance of windings 4-3 and 8-7, but only that the impedance of winding 21 be substantially equal to that of winding 6-5 and the impedance of winding 43-be substantially equal to that of winding 8-7. Arrangements'in accordance with the invention which will serve to balance the impedances of these windings to a degree which will reduce the noises referred to above .to anunobjection- .able amount are shown in Figs. 4 and 5.

In Fig. 4 is shown an arrangement of C- shaped and straight or I-shaped laminations of magnetic material, which may be used in the core 1 of Fig.1. Referring to Fig. 4, it will be noted that each layer of the core consists of two C-shaped and one I-shaped lamination, with the I lamination situated between the two C laminations, and that these layers are arranged so as toprovide; two complete air gaps 17 at each end of the I with respect to the center lines of the core.

core which are symmetrically distributed When used in the core of the repeating coil shown in Figs. land 2,-this symmetrical arrangement of the air gaps Will provide equal reluctances in the magnetic circuits at each end of the core, thus balancing the inductance of two equalwindings whenplacecl at either end of the core.

It has been found that if the laminations are assembled so that the air gaps 17 are of equal length, this arrangement will provide an impedance balance -between two end windings on the central limb of the core, either 21 and 6 5 or 4-3 and 8-7, as shown in Fig. 3, which will be substantially equivalent to the balance obtainable using a core structure without airaps. It has been found by experiment that in this type of on one end and on one side of tluncorc structure, and the remaining half are stacked so as to form two air gaps 19 at the opposite end and side of the core structure,

these air-gaps being symmetrical with re-' spect to the center lines of the core.

As in the arrangement of Fig. 4, it has been found that, if the laminations are assembled so that air gaps 18 and 19 are of equal length, the arrangement of F 5 will that the impedance'balance between wind- 1 ings may be adjusted within 1%.

A core employing the arrangement of C and I laminations illustrated in Fig.- 4 is ada ted especially to circuits car g relative y large values of superposed dir ct cur.- rcnt, as complete air gaps are obtained in such a core, the length of which may be readily adjusted. Also, such a core may be cheaply constructed and assembled. The core employing the arrangement of substantially closed S-type laminations illustrated in Fig. 5, however, is adapted especially for conditions where a maximum inductance is required in the repeating coil or transformer when relatively small values of superposed direct current are used, as only partially com lete air-gaps are. obtained.

A though the invention has been illustrated and described in connection with its use in telephone repeatingcoils, it is to be understood that it also may. be applied to any other types of inductance devices having shell-type cores, where a high degree of im-' pe'dance balance is desired between the windings when used to carryvarying values of superposed direct current.

It will be obvious that the general principles herein disclosed may e embodied in other inductance devices'widely diflereiit from those illustrated and without de arting from the spirit of the invention as de ned in the following claims.

What is claimed is:

1. In an inductance device, a magnetic core comprising a central branch and outer branches, a plurality of windingsvof equal impedances around said central branch, and

means to maintain the impedance balance between said windings "for-varying values of superposed direct current comprising airgaps in said core symmetrically arranged with respect to said windings. v

2. In an inductance device, a plurality of primary windin s of equal ondary windings of equal impedancesplaced and'a magnetic core therefor comprising a central branch and two outer branches in shunt therewith forming two magnetic, circuits of equal reluctances, said primary and secondary windings belng woundon said central branch of saidcore,

' said core having a. plurality .of air-gaps formed-through the magnetic circuit thereof symmetrically arranged with respect to the center-lines of said circuit, said. mag-' netic circuit effecting aniimpedance balance piece and two .tween said windings for w impedances e and a plurality of sec between said primary windings, and between ,said. secondary windings for varying values of superposed direct'current flowing therein.

3. In an inductance device, the combination With at least two primary windlngs placed side by side and having equal electriwards said straight leg, but spaced therefrom to form two equal air-gaps in each magnetic circuit including said straight leg and one of said C-shaped legs, said straight leg threading said primary and secondary windings, thereby effecting an impedance balance between said two primary windings and between said two secondary windings for varying values of superposed direct current flowingin said windings.

4. In an inductance device, the combination with a plurality of windings inductively balanced, of a core comprising a plurality of layers of magnetic material, each of said layers comprising an I-shaped shaped pieces in each layer facing in toward the Is iaped pieces but spaced therefrom so as toform a shell-type core having a central limb and two outer limbs, said windings being mounted side by side on said central limb, air-gaps on each side .of said central limb.

5. An inductance device comprising a C-shaped pieces,. said C- and said core having two equal i magnetic core having a central limb and two outer limbs forming two magnetic circuits in said core, and at least one pairof windlngs of. balanced lmpedances mounted side by sideon said central limb, said magnetic core comprising a plurality of C-shaped and I -shaped laminations, said C-shaped and I-shapeol laminations being so stacked as to form two air-gaps in each of said magnetic circults the air-gaps in said magnetic circuits being symmetrically arranged in said core, the reluctances of said 'magnetic circuits being thereby balanced so as to effect substantially perfect impedance balance bevarying values of superposed direct current therein.

6. n a transformer, the combination with at: least two electrically quivalent primary windlngs and at least two electrically equivalent secondary windings, of a magnetic core comprising a central limb and two similar .outer limbs comprising two magnetic cirtributed with respect to center-lil es of said core-whereby a high, degree of impedance central limb of said core for both the main,

, and leakage flux, for varying values of superposed :7. In a telephone repeating coil, the combination with at least two primary windings with equal electrical properties and at least two secondary windings with equal electrical properties, of a shell-type magnetic core comprising a central limb andtwo outer limbs forming two magnetic circuits, at least one of said-primary windings and one of said secondary windings being mounted on each end of said central limb, said central limb comprising a plurality of similar I-shaped pieces stacked together, said outer limbs each comprising a plurality of similar" direct current in sald windings.

C-shaped pieces stacked together, said C'- shaped pieces in each outer limb being arranged to face in toward said- I-shaped pieces in said central limb but spaced equally therefrom so as to form two air-gaps of equal size in each whereby the impedances of two equal primary windings on opposite ends of said central limb effectively balance each other with respect to both the main and leakage flux, and the impedances of two equalsecondary windings on opposite ends of said central limb effectively balance each ,other withrespect to both the main and leakage flux for any operating condition of superposed direct current in said windings. 4

In witness whereof, I hereunto subscribe my name this 10th day of December A. 1)., 1924.

A/RTHUR J. CHRISTOPHER-j of said magnetic circuits 

